Schooling fish, such as the rummy-nose tetra, depend heavily on visual cues to navigate their environment, interact with peers, and avoid obstacles. The availability of these visual cues, however, can be significantly influenced by changes in environmental conditions, such as light intensity. A recent study led by Dr. Guy Theraulaz from the Centre National de la Recherche Scienfique and colleagues from Beijing Normal University and the University of Toulouse explored the impact of varying light levels on the social interactions and collective behavior of these fish. Their findings, published in PLOS Computational Biology, offer new insights into how environmental factors can drive collective animal behavior.
The research team conducted a series of experiments analyzing the movements of rummy-nose tetras under different lighting conditions. The study combined empirical data with computational modeling to reconstruct and understand the interactions between individual fish and their environment.
“Our experiments demonstrate that light intensity strongly modulates social interactions between fish, influencing their collective motion patterns,” said Dr. Theraulaz. This modulation, he explained, occurs without altering the fundamental nature of the interactions but changes their strength and range, leading to distinct patterns of collective movement within fish groups.
Under low light conditions, fish displayed shorter, more frequent movements, possibly as a strategy to avoid collisions when visual information is limited. As light intensity increased, the fish took longer, more direct paths, interacting more strongly with both their peers and the boundaries of their environment. This behavioral shift highlights the critical role of visual information in maintaining group cohesion and navigating spaces.
In their simulations, the researchers found that as light intensity increased, fish tended to swim closer together and nearer to the tank walls. In smaller groups, this effect was more pronounced, leading to highly polarized swimming patterns, where all fish aligned and moved in the same direction. In larger groups, however, the fish exhibited a different pattern—forming a rotating “milling” structure around the tank’s center.
Dr. Theraulaz and his team developed a burst-and-coast swimming model based on the quantitative analysis of fish movements, focusing on how the fish’s interactions with their social and physical environment change with light intensity. The model successfully replicated the experimental observations, showing how light-induced changes at the individual level cascade into collective behaviors at the group level.
“The collective dynamics we observed in rummy-nose tetras under different light conditions suggest that environmental factors like light intensity can significantly influence social interactions,” Dr. Theraulaz noted. “Our work not only sheds light on the specific behaviors of schooling fish but also offers broader implications for understanding collective behavior in other animal species.”
This study underscores the importance of considering environmental variables when studying social interactions and collective behavior in animals. It also provides a foundation for future research into how other factors, such as water turbidity or temperature, might similarly influence group dynamics in schooling fish or other social species.
Journal Reference
Xue, T., Li, X., Lin, G., Escobedo, R., Han, Z., Chen, X., Sire, C., Theraulaz, G. “Tuning social interactions’ strength drives collective response to light intensity in schooling fish.” PLOS Computational Biology (2023). DOI: https://doi.org/10.1371/journal.pcbi.1011636
Images References
G. Theraulaz, CRCA, CBI
David Villa ScienceImage/CBI/CNRS, Toulouse
About the Authors
GUY THERAULAZ is a Senior Research Fellow with the National Center for Scientific Research (CNRS), and he is working at the Centre de Recherches sur la Cognition Animale in Toulouse, France. He received a Ph.D. degree at Aix-Marseille University and the Habilitation degree at Paul Sabatier University in Toulouse. He is an expert in the study of collective animal behavior and a pioneering researcher in the field of swarm intelligence. He is author of more than one hundred publications and five books, among which Swarm intelligence: From Natural to Artificial Systems (Oxford University Press, 1999) and Self-Organization in Biological Systems (Princeton University Press, 2001) are considered as reference textbooks. He was awarded the Bronze Medal of the CNRS in 1996.
CLÉMENT SIRE is a Senior Research Fellow with the National Center for Scientific Research (CNRS), and he is working at the Laboratoire de Physique Théorique in Toulouse, France. He graduated from the École Normale Supérieure (ENS) and he received a Ph.D. degree in Theoretical Physics at the Université Pierre et Marie Curie and ENS. He is an expert in Physics of society and Non-Equilibrium Statistical Physics. He is an outstanding referee of the American Physical Society since 2012 and was awarded the Bronze Medal of the CNRS in 1994.
XU LI and TINGTING XUE are PhD students at the School of Systems Science at Beijing Normal University who have also worked at the Centre de Recherches sur la Cognition Animale in Toulouse, France for 18 months. Their research interests include collective motion, phase transitions and critical phenomena, machine learning and turbulence. They have published several papers, including PLOS Computational Biology, Machine Learning: Science and Technology, Chinese Physics B, Physical Review Research, Europhysics Letters.
